Morphology and deformation behavior of “row-nucleated” polyoxymethylene film

Abstract

Abstract Crystallization from a stressed polymer melt produces not the familiar randomly nucleated spherulitic structures, but instead a highly oriented “row-nucleated” morphology. We have crystallized films of polyoxymethylene from stressed melts; just as polyethylene, the surfaces are covered with protruding lamellar edges highly oriented in the extrusion direction. There is no evidence for the more familiar spherulitic morphology. Electron microscopy directly revealed for the first time that the row nuclei are fibers, only about 200 to 300 A in diameter, extending for distances up to 10 mU. Although comprising a negligibly small amount of total sample volume, they are of prime importance in influencing how the sample will crystallize. Their presence determines, more than any other single factor, whether the sample will crystallize spherulitically or into a row-nucleated morphology. When deformed in the extrusion direction, the twisted lamellar bundles open up to form a fishnetlike structure. Simultaneo...